The present invention relates to intrusion detection barriers, and particularly to a deployable barrier, such as a coiled wire fence, equipped with means for detecting any attempted intrusion thereof.
Coiled wire fences, e.g., of the barbed wire or the razor foil type and sometimes called "concertina" fences, are widely used as deployable barriers which can be moved from one location to another according to the need, and also as an additionl barrier over another fence to give added protection in depth. It is desirable to equip such fences with intrusion detection sensors which will actuate an alarm or otherwise provide an indication when an intrusion of the barrier is attempted. One way of equipping deployable coiled wire fences with intrusion detectors is to provide them with vibration-type sensors which when subjected to vibrations over a threshold value sound an alarm. However, such systems tend to produce a large number of false alarms, e.g., because of the wind. Other systems include an arrangement which creates an electrostatic field within the coiled wire barrier, which electrostatic field is disturbed when an intrusion is attempted, but such systems are not only very expensive but also tend to produce a large number of false alarms. A still further proposed system includes microphones attached to the coiled wire fence, but such systems suffer from the same drawbacks of high expense and high rate of false alarms.
An object of the present invention is to provide a deployable or permanent intrusion detection barrier having advantages in the above respects. More particularly, an object of the invention is to provide a deployable intrusion detection barrier which is relatively simple and inexpensive to produce and to deploy, and which is characterized by a relatively low rate of false alarms, as compared to the above-mentioned systems.